Re: hook question

[Glenn Maynard <glenn@...>]

On Wed, Oct 11, 2006 at 09:22:29PM -0500, Rici Lake wrote:
> Thinking about that for a few more minutes, I realized that one could 
> eschew signals altogether in favour of a single alarm thread which woke 
> up every so often and sethook'd any lua_State's registered with it. In 
> that case, the thread safety of sethook would be an issue.
> 
> If it's not threadsafe as written (it looks ok to me, but as David 
> Jones says, it's hard to say for sure), then it cannot be fixed by 
> simply adding lua_lock and lua_unlock to it; that would make it 
> unusable in a signal handler, and moreover would not solve the problem 
> that was posed originally, because the entire VM runs inside the lock 
> and therefore the sethook wouldn't acquire the lock until the VM 
> released it (for example, by calling a CFunction), which might never 
> happen.

This is why I suggested separate signal and thread versions of
lua_sethook.

As for the VM releasing the lock: that's the purpose of luai_threadyield,
right?

-- 
Glenn Maynard